In general, an electric utility distribution system may be considered as a carefully tuned resonant energy pool, with generated electrical energy going into the pool in streams and consumed electrical energy leaving the pool in streams. Reliable operation (e.g., free of surges, stable voltage) can be achieved when the input electrical energy and the output electrical energy are substantially balanced. When a power generation system that feeds electrical energy to the grid exhibits substantial power output transients, the rest of the utility grid and distribution system may not have adequate time to adapt to the power level changes. As such, generator transients can contribute to grid instability.
For example, rapid changes in power output from one generator can cause other generators to warp or distort their outputs, which can result in voltage transients, voltage spikes, and/or undesired harmonic content. In some examples, this may lead to fault conditions at one or more substations in the grid. Such fault conditions can adversely affect both generators and consumers on the grid.
Accordingly, utility companies generally specify power generation standards that regulate the manner in which electrical power generators may deliver energy to the power grid and/or distribution system.
In some existing solar electric systems, solar arrays generate direct current (DC) electricity. To inject the electric energy onto the utility power grid, the generated DC energy is conducted via cables to a central point where it can then be converted to alternating current (AC) by large scale commercial inverters. Commercial inverters generally operate using high-frequency switch-mode technology to convert DC electricity to AC electricity. Such systems are believed to use a battery system to provide power regulation or to stabilize the AC voltage output during variations of DC power output by the solar arrays.